Bottom Line:
Two fundamental laser physics phenomena--dissipative soliton and polarisation of light are recently merged to the concept of vector dissipative soliton (VDS), viz. train of short pulses with specific state of polarisation (SOP) and shape defined by an interplay between anisotropy, gain/loss, dispersion, and nonlinearity.Emergence of VDSs is both of the fundamental scientific interest and is also a promising technique for control of dynamic SOPs important for numerous applications from nano-optics to high capacity fibre optic communications.Using specially designed and developed fast polarimeter, we present here the first experimental results on SOP evolution of vector soliton molecules with periodic polarisation switching between two and three SOPs and superposition of polarisation switching with SOP precessing.

ABSTRACTTwo fundamental laser physics phenomena--dissipative soliton and polarisation of light are recently merged to the concept of vector dissipative soliton (VDS), viz. train of short pulses with specific state of polarisation (SOP) and shape defined by an interplay between anisotropy, gain/loss, dispersion, and nonlinearity. Emergence of VDSs is both of the fundamental scientific interest and is also a promising technique for control of dynamic SOPs important for numerous applications from nano-optics to high capacity fibre optic communications. Using specially designed and developed fast polarimeter, we present here the first experimental results on SOP evolution of vector soliton molecules with periodic polarisation switching between two and three SOPs and superposition of polarisation switching with SOP precessing. The underlying physics presents an interplay between linear and circular birefringence of a laser cavity along with light induced anisotropy caused by polarisation hole burning.

f7: Pulse-to-pulse evolution of states of polarisation in the mode locked laser cavity.(a) green and red points corresponds to eigenstates of anisotropic cavity, circle is a trajectory of SOP evolution; (b) round trip is equal to the beat length (blue circle) and a half of beat length (green circles); (c) round trip is equal to one third of beat length (green circles); (d) pulse power is slowly oscillating and round trip is equal to one third of beat length (green circles).

Mentions:
As shown by Akhmediev, Soto-Crespo26 and Komarov et al.45, the eigenstates for a fibre with the linear birefringence and circular birefringence can be found as follows (Fig. 7 (a)): Here S0 = const and α is determined by the ratio of linear to circular birefringence strength. In our case, the linear and circular birefringenceis are controlled by the in-cavity polarisation controller. The rate of excitation migration is very high in LIEKKI™ Er80-8/125 used herein due to the high concentration of erbium ions and so the anisotropy induced by pump light is supressed4647. Polarisation hole burning46474849 changes the active medium anisotropy (both linear and circular) and so pulse SOP is located on a circle as shown in Fig. 7 (a). If pulse-to-pulse power is constant and the beat length in the anisotropic cavity is equal to the round trip distance then the pulse SOP is fixed and so vector soliton is polarisation locked3334 (Fig. 7 (b)). In the case of round trip distance being equal to half or third of beat length, the SOP is reproduced in two (Fig. 7 (b)) or three (Fig. 7 (c)) round trips; therefore, polarisation switching takes the forms shown in Figs. 3 (d) and 4 (d). The depth of the hole in the orientational distribution of inversion is proportional to the laser power and so with periodic oscillations of the output power (Fig. 5 (b)) light induced anisotropy in an active medium will be periodically modulated46474849. In this case, if the round trip is equal to the one third of beat length then SOP after three round trips will deviate slightly from the initial one as shown in Figs. 5 (d) and 7 (d) and can be reproduced only for the period of pulse power oscillations (Fig. 5 (d)). The same holds true for the case of two interleaved BSs with slightly different SOPs that results in superposition of the SOP switching with precession along the cyclic trajectory on the Poincaré sphere with the period of 14 round trips (Fig. 6 (c, d)).

f7: Pulse-to-pulse evolution of states of polarisation in the mode locked laser cavity.(a) green and red points corresponds to eigenstates of anisotropic cavity, circle is a trajectory of SOP evolution; (b) round trip is equal to the beat length (blue circle) and a half of beat length (green circles); (c) round trip is equal to one third of beat length (green circles); (d) pulse power is slowly oscillating and round trip is equal to one third of beat length (green circles).

Mentions:
As shown by Akhmediev, Soto-Crespo26 and Komarov et al.45, the eigenstates for a fibre with the linear birefringence and circular birefringence can be found as follows (Fig. 7 (a)): Here S0 = const and α is determined by the ratio of linear to circular birefringence strength. In our case, the linear and circular birefringenceis are controlled by the in-cavity polarisation controller. The rate of excitation migration is very high in LIEKKI™ Er80-8/125 used herein due to the high concentration of erbium ions and so the anisotropy induced by pump light is supressed4647. Polarisation hole burning46474849 changes the active medium anisotropy (both linear and circular) and so pulse SOP is located on a circle as shown in Fig. 7 (a). If pulse-to-pulse power is constant and the beat length in the anisotropic cavity is equal to the round trip distance then the pulse SOP is fixed and so vector soliton is polarisation locked3334 (Fig. 7 (b)). In the case of round trip distance being equal to half or third of beat length, the SOP is reproduced in two (Fig. 7 (b)) or three (Fig. 7 (c)) round trips; therefore, polarisation switching takes the forms shown in Figs. 3 (d) and 4 (d). The depth of the hole in the orientational distribution of inversion is proportional to the laser power and so with periodic oscillations of the output power (Fig. 5 (b)) light induced anisotropy in an active medium will be periodically modulated46474849. In this case, if the round trip is equal to the one third of beat length then SOP after three round trips will deviate slightly from the initial one as shown in Figs. 5 (d) and 7 (d) and can be reproduced only for the period of pulse power oscillations (Fig. 5 (d)). The same holds true for the case of two interleaved BSs with slightly different SOPs that results in superposition of the SOP switching with precession along the cyclic trajectory on the Poincaré sphere with the period of 14 round trips (Fig. 6 (c, d)).

Bottom Line:
Two fundamental laser physics phenomena--dissipative soliton and polarisation of light are recently merged to the concept of vector dissipative soliton (VDS), viz. train of short pulses with specific state of polarisation (SOP) and shape defined by an interplay between anisotropy, gain/loss, dispersion, and nonlinearity.Emergence of VDSs is both of the fundamental scientific interest and is also a promising technique for control of dynamic SOPs important for numerous applications from nano-optics to high capacity fibre optic communications.Using specially designed and developed fast polarimeter, we present here the first experimental results on SOP evolution of vector soliton molecules with periodic polarisation switching between two and three SOPs and superposition of polarisation switching with SOP precessing.

ABSTRACTTwo fundamental laser physics phenomena--dissipative soliton and polarisation of light are recently merged to the concept of vector dissipative soliton (VDS), viz. train of short pulses with specific state of polarisation (SOP) and shape defined by an interplay between anisotropy, gain/loss, dispersion, and nonlinearity. Emergence of VDSs is both of the fundamental scientific interest and is also a promising technique for control of dynamic SOPs important for numerous applications from nano-optics to high capacity fibre optic communications. Using specially designed and developed fast polarimeter, we present here the first experimental results on SOP evolution of vector soliton molecules with periodic polarisation switching between two and three SOPs and superposition of polarisation switching with SOP precessing. The underlying physics presents an interplay between linear and circular birefringence of a laser cavity along with light induced anisotropy caused by polarisation hole burning.